1. Field of Invention:
The present invention relates generally to composite materials and the building structural components made therefrom. More particularly, the present invention relates to composite structural panels made primarily of recycled synthetic and naturally-occurring materials and that are used to construct basic shelter, low-cost houses and other structures such as schools, churches, clinics, and external storage sheds.
2. Description of the Prior Art:
The world""s population is estimated at over six billion people. Within the next 20 to 25 years, that population is projected to exceed 10 billion. Population-induced problems exist world-wide, but are predominantly shared by those living in economically-distressed countries with large populations. One such population-induced problem includes substandard or a lack of basic housing and other building structures, such as clinics and storage facilities. The lack of basic housing and other structures in these countries has been addressed by using low-cost, pre-fabricated building components that are both durable and strong, in addition to being easy to assemble by local laborers having little training or experience in the construction trade.
U.S. Pat. No. 5,327,699, for example, discloses a flat, square-shaped panel module for use in assembling building structures. The panels are fabricated in one location and then delivered to a construction site for assembly into floors, walls, roofs and roof trusses to produce various sized building structures. Their flat, square shape reduces shipping costs and facilitates shipping overseas, making them attractive for use in areas where traditional U.S. construction materials and techniques may not be readily available. Some of the panels may include conduits or channels for electrical and plumbing works. Each panel includes an inner and outer surface filled with foam insulation. The patent discloses panels made from, among other things, recycled products such as ceramic, glass, plastic and aluminum. One disadvantage of the disclosed flat panel modules is that most of the strength of the modules is provided by one or more load-bearing members running through the center of the panels or along the edges of the panels. The foam insulation interior layer provides little weight-bearing support.
Some modular systems are designed to be partly assembled at the construction site. U.S. Pat. No. 5,974,751, for example, discloses a hollow, thermoplastic, interlocking structural component that may be filled with concrete at the construction site to form building elements such as walls. The structural components may be made of reprocessed (or recycled) plastic and conduits may be included in the structural components by inserting pipes before pouring the cement. Although using light-weight plastic forms like those disclosed in this patent can reduce shipping costs and are relatively simple to assemble by untrained laborers, a source of concrete must be provided at the site and skilled labor must be available to produce the finished structural members. Thus, in certain parts of the world, these forms may not be used to address basic shelter, low-cost housing needs.
As noted above, specialty structural modules can be fabricated having integrated utility conduits for electrical wires, plumping and ventilation, which reduces on-site labor and construction costs. U.S. Pat. No. 6,308,465, for example, discloses a rectangular, pre-cast module containing existing utility systems and coupling elements for fastening to other utility modules. The panels may include portions made of various polymeric substances, including polyurethane, polyisocyanate and polyurethane-polyisocyanurate structural foams. A suitable mixing device or mold is used to produce the plastic components. The fabricated modules are then shipped to a construction site and placed on a foundation as part of the construction of a building.
To reduce the cost of modular building panels, recycled materials are often used in addition to other additives. U.S. Pat. No. 6,044,604, for example, discloses a composite roofing board having a paper layer made of recycled paper fibers. Glass strands or glass fibers are also disclosed as possible components of the panels. U.S. Pat. No. 5,718,096 discloses using recycled materials and glass fibers in composite panel elements for use in building structures. U.S. Pat. No. 6,322,731 discloses the use of rice husks, wheat husks and sawdust in forming constructions panels.
Many of the above-identified patents disclose panels made of layers of various materials: a bottom and top layer and one or more inner layers sandwiched between the outer layers. One advantage of using layered composite panels for building structures like houses is that the layers can, depending on the layer material used, provide dimensional stability, heat transfer resistance and an aesthetic appearance. U.S. Pat. No. 5,483,778, for example, discloses a layered, modular construction panel having dimensional stability and aesthetic surface features. One disadvantage of layered panels is that the manufacturing method can be costly and complicated compared to other manufacturing methods, like extrusion, pultrusion, and compression of polymeric materials.
As noted above, the advantages and disadvantages of pre-fabricated, modular construction panels are numerous. U.S. Pat. No. 6,322,731 states that the use of composite panels can achieve a desired strength-to-weight characteristic and provide thermal and acoustic insulation properties satisfying basic housing needs. However, a major problem with known fabrication techniques is that there is a practical limit to the maximum length of the individual panels that can be used for floors, walls and roofs. That in turn leads to the requirement for smaller panels to be joined end to end to form a combined panel assembly of the necessary size. Typically, however, it has been identified that inadequate techniques for joining the panels have resulted in such structures being relatively weak. The resultant loss of structural integrity has, in turn, resulted in the potential strength characteristics not having been realized in larger scale applications, particularly for use in housing. For that reason, composite panels have tended only to be used to form internal partitions and non-load bearing walls, where significant structural integrity is not required. Accordingly, as noted in U.S. Pat. No. 6,322,731, a separate framing structure is still required and the inherent problems associated with conventional building methods have remained largely unsolved.
In view of the foregoing, it should be apparent that there exists a need for a low-cost composite building material that can be formed into building structural panels using a relatively simple and inexpensive manufacturing process, such that the panels have adequate dimensional stability, durability and flexibility features making them ideal for constructing low-cost, basic housing structures in locations around the world.
Accordingly, it is a principal object of the present invention to provide a composite material that is composed primarily of recycled polymer composite material, including polyolefins such as polyethylene and polypropylene.
It is another object of the present invention to provide a composite material that is composed of recycled polymer composite material and various additives to increase the strength, flexibility, durability, and permanence of the composite material.
It is still another object of the present invention to provide a composite material that includes various amounts of other natural or synthetic recycled or virgin substances in proportions that will contribute to the structural integrity or other features of the material.
It is another object of the present invention to provide a structural panel made of a low-cost, easy to manufacture, composite material such that the structural panel is modular but retains an adequate level of versatility.
It is still another object of the present invention to provide a structural panel made of a composite material using various plastic forming manufacturing technologies, including, but not limited to, compression, injection-compression and extrusion.
It is another object of the present invention to provide a structural panel of sufficient thickness and rigidity to constitute vertical weight-bearing walls or horizontal ceiling or floor structures.
It is still another object of the present invention to provide a structural panel having common structural features for simplifying the assembly process.
It is another object of the present invention to provide a structural panel that can be attached to other structural panels to form a building, such that the assembling of panels requires minimal training, education, tools and other resources.
It is still another object of the present invention to provide a structural panel that can be rapidly attached to other structural panels to permit the fabrication of a single structural unit in approximately one day by a team of three to five people.
Briefly described, these and other objects and features of the present invention are accomplished, as embodied and fully described herein, by a composite material that is formed into basic structural panels that can be subsequently assembled into the floors, walls, roof trusses, and roofs of buildings by unskilled labor having access to basic tools. Thus, basic shelter, low-cost houses and various other structures, such as schools, churches, clinics, and storage facilities, may be constructed. The building material for the panels is a molded polymer composite, made from either homogeneous or non-homogeneous materials. The material consists primarily of recycled polyolefins, primarily polyethylene and polypropylene compounds with or without various additives being added, including glass fiber, metals and naturally-occurring materials such as rice husks, sugar cane bagasse, nut shells, talc, clay, sand and wood. Other polymeric compounds and additives may also be used.
The structural panels made from the composite material are fabricated using various plastic forming techniques, including, but not limited to, compression, injection-compression, extrusion, and pultrusion, in a mold. Those processes are capable of providing durable structural panels of sufficient strength and density for many different applications, like those noted above. The basic structural panel is common to all single-unit and multiple-unit structure configurations, which can be produced from variants of the same mold, thus reducing manufacturing costs. However, minor differences in the structural panels provide increased versatility. For example, some of the panels may be modified to include conduits for electrical wiring, plumbing and ventilation and a cross-ribbed reinforcement grid may be included for strength. As formed, the basic structural panel may be made into wall panels, mitered wall panels, floor panels, roof/ceiling panels, and roof truss panels.
Each structural panel may be provided with flanges at their edges in which there are holes that align with holes on other structural panels for fastening the structural panels together using various fasteners. Sealants or adhesives may be applied to the interfaces between the structural panels. Vertical or horizontal rods may also be placed to run through the available channels formed in the composite material to enhance structural stability.
The method of the present invention is carried out by providing pre-fabricated structural panels for assembly into a low-cost, simple to assemble building structures; providing a simple schematic capable of being understood by people of different languages having, in some instances, little literacy skills; fastening the various structural panels together to form a floor, walls, and a roof; and fastening the floor, walls and roof together to form a basic, low-cost shelter.
With these and other objects, advantages and features of the invention that may become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several drawings attached herein.